DE60220728T2 - Device for temperature measurement - Google Patents

Description

Imaging devices to create images on media by ejecting colorants onto media one or more printheads. The printheads include arrays of nozzles that chambers coupled with openings exhibit. In addition to the chambers are resistive Elements for heating the ink to cause the ink in the chambers from the Nozzle is ejected. The quality of the outcast Ink generated image is characterized by the uniformity of the quantity of the nozzles expelled Ink influences. The uniformity of the quantity of the nozzles expelled Ink is affected by the temperature of the chambers. One up the temperature related adjustment of the supplied to the resistors Performance may vary from quantity to temperature Nozzles of ejected ink and changes at least partially compensate for the operating temperature of the printhead. Inaccuracies regarding Measuring the temperature of the printhead can increase the effectiveness of the compensation of temperature-related changes the quantity from out of the nozzles outcast Reduce ink.

The EP 0 752 313 A2 discloses an ink jet printhead comprising a plurality of ejection resistors and at least one additional resistor integrated on the same semiconductor substrate. The additional resistance is formed by a material having a positive resistance variation coefficient with a temperature between 0.3 and 1.0% / ° C, and is used for both heating a semiconductor substrate and measuring its temperature (T _S ).

The US 5,208,611 discloses a heating device for an ink jet printer equipped as a heating resistor in the form of a heating line meandering structure directly by an electrically conductive thin film. The heating resistor is a component of a resistance measuring bridge and is simultaneously used as a heat source and as a temperature sensor on the basis of a processing and evaluation of its electrical resistance values at different times.

The US 5,745,130 discloses a temperature controlled oscillator formed on a printhead. The oscillator includes a resistor whose resistance varies in proportion to temperature variations of the printhead.

SUMMARY OF THE INVENTION

A Device comprises a substrate and a resistive element, arranged on a first region of the substrate and made of a first material that has a first temperature coefficient of the specific Resistor is formed. In addition, the device includes a pair of webs coupled to the resistive element and each of which consists of a first plurality of sections a second material having a second temperature coefficient of the resistivity, and a second plurality of sections of a third material that has a third temperature coefficient of the resistivity is formed.

DESCRIPTION OF THE DRAWINGS

One more comprehensive understanding of exemplary embodiments of the temperature measuring system results from consideration of the following detailed Description taken in conjunction with the accompanying drawings is taken, where:

In 1 an embodiment of an ink jet printer is shown that includes a printhead that uses an embodiment of the temperature measurement system.

In 2 a high-level block diagram of one embodiment of an ink-jet imaging device using an embodiment of the temperature measurement system is shown.

In 3 a high-level schematic diagram of one embodiment of the temperature measuring system is shown.

In 4 a schematic diagram of a part of the temperature measuring system is shown.

In 5A and 5B alternate embodiments of webs ge shows that could be used in embodiments of the temperature measuring system.

DETAILED DESCRIPTION OF THE DRAWINGS

Although embodiments of the temperature measurement system are disclosed in the context of one embodiment of an ink jet printer, it should be understood that embodiments of the printhead could be usefully applied to other types of imaging devices. Embodiments of the temperature measurement system are applicable to a variety of imaging devices utilizing thermal inkjet technology. For example, embodiments of the temperature measurement system could be used to improve the performance of large format ink jet plotters, fax machines that use thermal inkjet technology, Copiers that use thermal inkjet technology, ink jet imaging devices that perform port erasures, or ink jet imaging devices that make markings on packages. In general, embodiments of the temperature measurement system can be usefully applied to imaging devices that use one or more printheads to produce a colorant, e.g. As ink, eject on surfaces. Although one embodiment of the temperature measurement system will be discussed in the context of an ink jet printer employing a movable printhead, embodiments of the temperature measurement system may be usefully employed in ink jet printers having fixed printheads. Although an embodiment of the temperature measurement system will be discussed in the context of a color ink jet printer, it will be appreciated from the information in the present disclosure that embodiments of the temperature measurement system can be usefully applied to a monochrome ink jet imaging device.

Ink jet imaging devices such. As printers, large format plotter / printer, fax machines and copiers are now widely accepted. These imaging devices are described by WJ Lloyd and HT Taub in " Ink Jet Devices ", Chapter 13 of Output Hardcopy Devices (Ed. RC Durbeck and S. Sherr, San Diego: Academic Press, 1988), and in U.S. Patent Nos. 4,150,199; U.S. Patent Nos. 4,490,728 and 4,313,684 described. The basics of this technology are also disclosed in several articles in several editions of the Hewlett-Packard Journal [Vol. 39, No. 5 (May 1985), Vol. 39, No. 4 (August 1988), Vol. 39, No. 5 (October 1988), Vol. 43, No. 4 (August 1992), Vol. 43, No. 6 (December 1992 and Vol. 45, No. 1 (February 1994)]. Inkjet image forming apparatuses can produce high quality images on media, are generally compact and portable, and produce images on media quickly and quietly since only ink touches the medium.

A Ink jet imaging device such. B. an inkjet printer creates an image by making a pattern of individual ink drops in certain places one for the medium defines defined arrays on the medium. The posts represents you expediently as small dots in a rectilinear array. These places become common referred to as pixels. The image forming process may be considered filling a Pixel pattern can be viewed with ink drops.

Inkjet imaging devices to fill Turn the pixels off by placing very small drops of ink on the medium eject and they usually include a movable carriage carrying one or more print heads of each of which has ink ejection nozzles. The car crosses the surface of the medium, and the nozzles are controlled thereat according to a command of a microcomputer or another controller at appropriate times, ink drops eject, wherein the timing of application of the ink drops is the pixel patterns of the picture being created.

Of the typical inkjet printhead (i.e., a silicon substrate, the a plurality of thin film layers, formed on the substrate structures and connections to the substrate has liquid) Ink (i.e., dissolved Colorants or pigments dispersed in a solvent). He has an array of precise formed openings or Nozzles open, attached to a printhead substrate which is an array of Ink ejection chambers includes, the liquid Receive ink from the ink reservoir. Each chamber is located opposite the nozzle, so that ink can accumulate between it and the nozzle. The ejection of ink droplets is usually done under the control of a microprocessor whose signals pass through electrical traces are routed to the ink ejection element. The Ink ejection element comprises a firing resistor. When electrical pressure pulses to the Firing resistor are delivered, a small part evaporates the ink next to it and bump one Drops of ink from the printhead. Formally arranged nozzles form a matrix pattern. A proper sequencing of the operation every nozzle causes characters or images to be printed on the media be while the printhead moves past the medium. The quantity of one expelled Ink drops could based on the volume of the ejected ink drop on the Base of the mass of the expelled Ink drop or on the basis of the weight of an ink drop be measured. Usually a measurement is made of a quantity of an ejected ink drop in terms of mass. Therefore, the present specification discusses the operation of embodiments of the temperature measuring system with respect to the mass of ejected ink drops.

The ink cartridge containing the nozzles is repeatedly moved across the width of the medium on which the image will be formed. At each of a stated number of increments of this movement across the medium, each of the nozzles is caused to either eject ink or not eject ink, depending on the output produced by the controlling microprocessor. Each completed movement across the medium can apply ink to pixels, forming a ribbon which is about as wide as the number of nozzles arranged in a column of the ink cartridge times the distance between nozzle centers, the tape being as long as the dimension of the medium parallel to the direction of relevant movement between the medium and the medium Printhead runs. After each such completed tape, the media is advanced by the width of the tape, and the ink cartridge begins the next tape. Proper selection and timing of the signals produces the desired image on the medium.

at an inkjet printhead becomes ink from an ink reservoir, integrated into the printhead, or from an "off-axis" ink reservoir, the above Lines connecting the printhead and the reservoir, the printhead Ink feeds supplied. Subsequently, will Ink either through a in the middle of the bottom of the substrate formed oblong Hole, "central Feeder "or um the outer edges of the substrate, "edge feed", the various Ink ejection chambers fed. In the middle supply flows the ink then into a central slot through a central slot in the substrate Distributor area, in a barrier layer between the substrate and a nozzle member formed is, then into a plurality of ink channels and finally into the different ink ejection chambers. When the edge feed flows Ink from the ink reservoir around the outside edges of the substrate in the ink channels and finally into the ink ejection chambers. Both in the central feed and in the edge feed supplies the flowpath from the ink reservoir and manifold in an inherent manner restrictions the flow of ink to the ink ejection chambers.

Color inkjet imaging devices typically use a plurality of print cartridges, usually two to four, which are mounted in the printer carriage to a complete spectrum to create colors. For a four-cassette printer, each one contains Print cartridge an ink of a different color, the usual used basic colors are cyan, magenta, yellow and black. at A cartridge with two cartridges may have one cartridge of black ink with the other cassette being a three-cell cassette, which contains the inks of the primary colors cyan, magenta and yellow, or it can alternatively two two-cell cassettes can be used to make the to contain four colored inks. Furthermore, two three-cable cassettes used to contain six primary color inks, e.g. Black, cyan, magenta, yellow, light cyan and light magenta. Besides, you can ever according to the number of different base color inks that used should be used, other combinations.

The Basic colors are required by applying a drop Color produced on a pixel spot on the medium while secondary colors or shaded colors by applying several drops of different colors Primary color inks on the same or an adjacent pixel location are formed, the overprinting two or more primary colors the secondary colors according to accepted optical principles generated.

At the a color printing process, the various colored ink drops, which are ejected by each of the print cartridges, selectively overlapping, to create sharply contoured images that come from virtually everyone any color of the visible spectrum. To a single To produce pixels on a medium having a color which a mixture of two or more of the colors required by Different print cartridges are supplied, the nozzle plates on each of the cassettes be precisely aligned so that a from a selected one Nozzle in ejected from a cassette Drop one drop from a corresponding nozzle in one ejected other cassette is overlapped.

The Print quality generated by an ink jet device depends on the reliability and drop quantity repeatability their ink ejection chambers. A multi-pass print mode may reduce the effect of the defective ink ejection elements on the print quality partially relieve. The concept of print modes is a useful and well-known technique, with each pass of the printhead only a fraction of that required in each section of the image accumulate all the ink, so that any areas, at each Pass white leave be completed by one or more later runs. By reducing the amount of liquid which is on the page at any time, this tends to flow, To limit blocking and waviness.

The specific partial inking pattern used in each pass, as well as the manner in which these various patterns together form a single, fully inked image, is known as a "print mode." Print modes allow a compromise between speed and image quality Presentation mode, also known as best mode, is slow but produces the highest image quality.A normal mode is a compromise between design and presentation modes.Print modes allow the user to switch between These compromises allow the printer to have several factors that affect image quality during printing flow, including: 1) the amount of ink placed on the media per pixel location, 2) the speed at which the ink is placed, and 3) the number of passes required to complete the image to complete. Providing various print modes to allow for placement of ink drops in multiple tapes can aid in hiding nozzle defects. Various print modes are also used depending on the media type.

For increased throughput on plain paper media, single pass mode operation is used. Using this mode on certain other types of paper media, such as paper. Coated paper, results in dots resulting from the ink drops that are too large. In a single pass mode, as the printhead passes across the belt, ink drops are placed on all pixels to which ink is to be applied to the belt. Then the medium is advanced to the position for the next tape. In a two-pass print mode, one-half of the ink-available pixels on the pixel lines making up the tape are applied over the tape on each of two passes of the printhead. Therefore, two passes are needed to complete the ink application for this tape. Similarly, a four-pass mode is a method of placing ink droplets on pixels, wherein on each of four passes of the printhead across the tape, one quarter of the pixels to which ink is to be applied to the tape is applied. Further, an eight-pass mode is an ink-to-pixel method in which one-eighth of the pixels to which ink is to be applied to the tape is applied on each of eight passes of the printhead across the tape. For example, multi-pass thermal ink-jet printing is communicated in the shared U.S. Patents 4,963,882 and 4,965,593 described. Generally, to complete the imaging process, it is desirable to use the minimum number of passes for each tape to maximize printer throughput and reduce unwanted visible printing artifacts.

Regarding one Creating an image on a medium is the color of a region of the picture on the quantity each of the different colors related to the image be used in the field. In a small region of the produced Picture that includes a relatively small number of pixels depends on the color perceived by this region from the relative quantity of the different Colors of ink drops applied to the pixels. Consider the formation of a neutral gray color in the region by the Application of predetermined quantities of cyan ink, yellow ink and magenta ink. Located in the L * a * b * color space the neutral gray color region at the intersection of the a * and the b * -axis along the L * -axis. With the right quantities everyone the one expelled from the region cyan ink, yellow ink and magenta ink the resulting color of the region is at the neutral gray point (the intersection of the a * -axis and the b * -axis), as intended is.

Generally changed the quantity from a printhead nozzle expelled Ink drops when the temperature of the structure, which is the Nozzle assigned Ink ejection chamber surrounds, changes. Generally increased the mass is ejected Ink drops when the temperature of the ink ejection chamber increased surrounding structure. The underlying physical effects that tend to the mass expelled To increase ink drops, involve changes the surface tension the ink, changes the ink viscosity and changes of for blister nucleation available standing energy. Everyone works to form the aforementioned neutral gray region cyan, magenta and yellow printheads or near a nominal operating temperature such that when control signals, the an output of Amounts of ink that are necessary to neutralize in the region to form gray color, to be delivered to the respective printheads are the respective printheads the ink quantities actually emit on the pixels, necessary to form a neutral gray color region.

The Speed at which signals are delivered to resistors that cause the Ink ejection chambers are assigned, affects the temperature of the substrate of the printhead. For one Printhead where no attempt is made to temperature stabilize the substrate, the temperature of the substrate while Change the use of the printhead considerably, depending on changes the firing frequency of the nozzles over the Time away. In a certain region of the printhead, a localized heating of the Substrate from firing nozzles with a larger frequency respectively. The effect of the local limited warming can because of the greater thermal resistance over the Substrate of the larger print heads compared to smaller print heads easier on larger printheads done as with smaller print heads. If concerning this temperature changes not at least some compensation, can be a perceptible Deterioration of print quality result.

Consider the fact that the operating temperature of the magenta printhead over the nominal operating temperature increases. This can be done, for example, due to an increased firing frequency of the magenta printhead. As a result of the temperature rise of the ink ejection chambers in the magenta printhead, the mass of a magenta ink drop ejected from nozzles in the magenta printhead increases beyond the mass necessary (in combination with those ejected from the yellow printhead and the cyan printhead Ink drops) to create the neutral gray color of the region. Due to the applied excessive amount of magenta ink, the hue of the generated region shifts toward the magenta hue. Similarly, fluctuations in the ejected mass of ink drops can cause undesirable shifts in color intensity and luminance of regions. Also, look at a picture that includes sharp edges. The increase in the mass of ejected ink drops can reduce the sharpness of the edges when the image is formed on paper.

A variety of techniques are used to compensate for the change in ejected ink quantity with temperature. One way to compensate for the change in ejected ink quantity with temperature is to provide one or more heaters to heat the substrate. Heating the substrate reduces the amount of temperature change that the printhead experiences as the firing frequency of the nozzles changes. The temperature of the substrate is measured and compared to a target value. Depending on the temperature difference between the measured substrate temperature and the target substrate temperature, the power delivered to the substrate heater is changed (taking into account the heating that occurs from firing nozzles) to decrease the amount of the difference. More information about this technique can be found in the U.S. Patent Nos. 5,736,995 and 5,673,069 both of which have been transferred to Hewlett-Packard.

A Another technique that compensates for a temperature change the ink drop compound is used, is the mass Ink coming out of the nozzles pushed out will, depending to change from the temperature. In this technique, a measurement of the substrate temperature is used about the quantity the one out of the jets over one Region expelled To adjust ink in a manner (eg, by temperature dependence a halftoning operation) showing the temperature dependency in terms of the quantity of from the nozzles expelled Ink compensates. The effectiveness of both techniques to a temperature change Compensating for the ink drop mass is done by a precise measurement the temperature of the temperature of the substrate improved.

Around an ejection of Ink from nozzles To achieve in a printhead must be for a limited time interval a minimum amount of energy applied to a firing resistor to quickly vaporize ink and eject ink from a nozzle. If the while the energy delivered to the firing resistor increases over the time interval, also takes the quantity at the outcast Ink until a limit is reached, beyond which the mooring additional Energy during of the time interval, the amount of ejected ink is not essential changed. The while The energy required by the limited time interval depends on the temperature of the structure, which is an ink chamber associated with the nozzle surrounds. As the temperature of the surrounding structure increases the energy that needs to be applied to the firing resistor to eject ink cause, off. Usually is the while of the time interval supplied to the firing resistor energy a little bit higher as the minimum amount of energy that is required to output the maximum Effect of ink. This amount of energy increases with increasing Temperature of the structure surrounding the ink chamber. Because of reliability it is desirable the smallest possible To supply energy to the firing resistors to achieve the maximum output To achieve ink quantity.

A Way, the amount of energy delivered to the firing resistors is controlled by adjusting the pulse width of the applied Driver signal as a function of the measured temperature of the substrate. To the firing resistors delivered energy precisely Setting near the ideal level is a precise measurement of the temperature of the substrate in the region near the nozzles for which the energy is delivered, helpful. This can become a more difficult task if due to the physical size of the substrate considerable Temperature differences detected between different regions on the substrate can be. This may be the case if the printhead includes multiple regions, each having a plurality of nozzles and associated firing resistors.

In 1 is an embodiment of an image forming apparatus, a color ink jet printer 100 , which comprises an embodiment of the temperature measuring system. The color inkjet printer 100 includes a cover 102 , a media input tray 104 to hold media 106 to be used in an image forming process, a media output tray 108 to record the units of media 106 . on which images were produced, color ink cartridges 110 (including a cyan cassette 110a , a magenta (M) cassette 110b , a yellow (Y) cassette 110c and a black (K) cassette 110d ) and a motor car 112 to slide along a slide bar 114 while colorant from one or more of the color cassettes 110 is placed on pixels. In the color inkjet printer 100 includes this in the color cassettes 110 Stored colorant ink. Printheads in a cyan cassette 110a , a magenta (M) cassette 110b , a yellow (Y) cassette 110c and a black (K) cassette 110d are included, implement parts of the temperature measuring system.

In 2 Figure 4 is a block diagram illustration of one for creating images on media 106 used system. The system includes a computer 200 , The computer 200 can run an application program to generate data that is on a monitor 202 (e.g., a CRT (cathode ray tube)) displayed image, or the data corresponding to the image from a storage device included in the computer 200 is included by the application program to regain. Usually, the monitor shows 202 an image using an RGB color space and 24 bits (8 bits for each primary color) to set the color value for each monitor pixel. An embodiment of an image forming apparatus, an inkjet printer 204 is with the computer 200 coupled.

The printer 204 Can the color inkjet printer 100 or other types of inkjet imaging devices. the printer 204 includes the ability to form color images on a medium using a set of colorants (eg, ink or toner) that form a color space (eg, cyan, magenta, and yellow and optionally black) 106 to create. The printer 204 may be configured to produce images at 300 dpi, 600 dpi, 1200 dpi or other resolutions. A printer driver program that is in the computer 200 , converts the data (corresponding to the image) received by the application program into a form that is passed through the printer 204 is usable, for. For example, a page description language (PDL) file. For example, the PDL file may include a file defined in the HEWLETT-PACKARD PCL-3 or PCL-5 format.

The printer 204 prepares the PDL file to generate pixel data that includes a color value for each pixel of each of the color planes that form the image. For example, an embodiment of the printer 204 Create color values for pixels that form the cyan, magenta, yellow, and black color planes. For example, the color values for each of the pixels in the color planes may be between 0 and 255. A halftoning process may be performed on the color values of the color planes to produce halftone data for the image. The halftone data comprises binary data defining for each of the pixels in each of the color planes whether a colorant for that color plane is placed on the pixel. Alternatively, the image may be generated using the color values for each of the pixels in each of the color planes without halftoning. In this alternative, the amount of colorant placed on the pixel is directly related to the color value for the pixel. In an ink-jet image forming apparatus, the amount of colorant is controlled by the number of ink drops of a specific color placed on the region of the medium corresponding to the pixel. In the printer 204 is an embodiment of an image forming mechanism, an image forming mechanism 206 , contain. The imaging mechanism 206 Includes the hardware necessary to apply colorant to a medium 106 to place.

An embodiment of a controller, such as a controller 208 that with the imaging mechanism 206 coupled, controls the placement of colorant on a medium 106 using the imaging mechanism 206 which uses the contone data or color values for the pixels forming each color plane. The output from the printer driver software included in the computer 200 expires, is through an interface 210 to the controller 208 directed. The control 208 includes the ability of the computer 200 to prepare the received PDL file to generate pixel data for each of the pixels forming the image. The control 208 includes an embodiment of a processing device, e.g. B. a processor 212 configured to execute firmware or software, or an application specific integrated circuit (ASIC) for controlling the placement of colorant on a medium 106 by means of the imaging mechanism 206 , In addition, the controller includes 208 an embodiment of a storage device, for. B. a memory 214 for storing halftone data or color values for the image forming pixel. The processor 212 further comprises a configuration to execute a code for performing an embodiment of the temperature measuring system.

The imaging mechanism 206 includes one or more ink cartridges for which an ink cartridge 216 is exemplified, which is movably mounted on a carriage, whose position by a belt, by a Schrittmo driven, is precisely controlled. An ink cartridge driver circuit coupled to the controller and the ink cartridges fires nozzles on printheads for which a printhead 218 by way of example and contained in the ink cartridges based on signals received from the controller, to colorant the medium according to the halftone data or color values for the pixels forming each of the color planes 106 to place. The printheads included in these ink cartridges include hardware associated with an embodiment of the temperature measurement system described later in the present specification. Further details regarding embodiments of imaging mechanisms used in color inkjet printers can be found in US Pat U.S. Patent No. 6,082,854 entitled MODULAR INK-JET HARD COPY APPARATUS AND METHODOLOGY, issued to Axtell et al. and assigned to the Hewlett-Packard Company, and in the U.S. Patent No. 5,399,039 entitled INK-JET PRINTER WITH PRECISE PRINT ZONE MEDIA CONTROL, granted to Giles et al., and assigned to the Hewlett-Packard Company.

In 3 3 is a high-level schematic diagram of one embodiment of the temperature measurement system implemented on an embodiment of a printhead. The printhead is on a substrate 300 educated. Although this in 3 For clarity, for illustrative purposes, the substrate comprises 300 the structures of a typical printhead such. Ink delivery slots, ink ejection chambers, firing resistors, etc. Regions 302 . 304 . 306 and 308 each include an array of nozzles and associated firing resistors for ejecting ink. Resistive elements 310 . 312 . 314 and 316 are formed of a material with a known temperature coefficient of resistivity. The resistive elements 310 . 312 . 314 and 316 are arranged so that they each have the temperature of the local region of the substrate 300 on which they are placed accept. Embodiments of power sources, eg. B. Power sources 318 . 320 . 322 and 324 , are configured to provide electrical power to the resistive elements 310 . 312 . 314 and 316 to deliver. Each of the power sources 318 . 320 . 322 and 324 provides a substantially constant and known current to the resistive elements 310 . 312 . 314 respectively. 316 when power is applied to them. The result of applying power to each of the resistive elements 310 . 312 . 314 and 316 resulting voltage changes according to temperature-related changes in the resistance, providing signals related to the temperature of the regions. power sources 318 . 320 . 322 and 324 are by connecting tracks, for which a train 326 is representative of the resistive elements 310 . 312 . 314 and 316 coupled. The webs provide an electrical connection between the resistive elements 310 . 312 . 314 and 316 and the power sources 318 . 320 . 322 and 324 , In addition, webs provide an electrical connection between an analog-to-digital converter 328 and the tracks, the electricity from the power sources 318 . 320 . 322 and 324 to the resistive elements 310 . 312 . 314 and 316 to lead. How out 3 As can be seen, in this particular implementation of a printhead, a significant track length is used to drive each of the resistive elements 310 . 312 . 314 and 316 to connect with its corresponding power source.

An embodiment of a measuring device, for. B. analog / digital converter 328 , Includes 4 channels, each receiving a voltage value that is applied to the over resistive elements 310 . 312 . 314 and 316 applied voltage resulting from the flow of current is related. The A / D converter 328 converts each of the voltages it receives into corresponding digital values. It should be understood that other embodiments of power sources and measuring devices could be used to generate the digital values. For example, embodiments of the power source could include voltage sources to provide substantially constant voltages across the resistive elements to the resistive elements 310 . 312 . 314 and 316 to deliver. Further, an embodiment of the measuring device (eg, a current-to-voltage converter) could include a current measuring device that would provide voltage values corresponding to currents flowing from the voltage sources to the resistive elements 310 . 312 . 314 and 316 to be delivered. Then digital values would be determined from these voltage values. These digital values are determined by an embodiment of a processing device, processor 330 , received. The processor 330 converts, either by using lookup tables or computationally, that of the analog to digital converter 328 received digital values into digital values that match the temperatures of the substrate 300 near the regions 302 . 304 . 306 and 308 in relationship. The application of firing pulses to the firing resistors causes a change in the resistance of those resistive elements 310 . 312 . 314 and 316 to which firing pulses have been applied. As by the corresponding of the power sources 318 . 320 . 322 and 324 supplied current remains substantially constant during application, the temperature-induced resistance change resulting from the application of firing powder results in a change in the voltage resulting from the application of the current sources across the tracks and resistive elements. The digital values are used to determine the absolute temperature. By comparing the digital values, after applying pulses to the firing resistors, and before applying pulses to the firing resistors, a measurement of the temperature change of regions of the substrate 300 be determined. Using these temperature related digital values, the processor operates 330 an embodiment of a temperature compensation system. An embodiment of the temperature compensation system may adjust the pulse width of the drive signals applied to the firing resistors such that the temperature of the substrate 300 is controlled substantially at a desired temperature. Another embodiment of the temperature compensation system may be used to provide resistive heating elements associated with the substrate 300 thermally coupled, to control, so that the temperature of the substrate 300 is controlled substantially at a desired temperature. Yet another embodiment of the temperature compensation system may be used to control an amount of ink applied to a region in response to the measured temperature. In addition, other embodiments of the temperature compensation system could be implemented that combine control of several of the aforementioned performance aspects.

As previously mentioned, the resistive elements could 310 . 312 . 314 and 316 be formed of a material having a known and predetermined resistivity and temperature coefficient of resistance, for. As aluminum or a tantalum / aluminum alloy. In addition, the power sources 318 . 320 . 322 and 324 configured to provide a known amount of power. By knowing how the resistance varies with the temperature and the amount of the resistive elements 310 . 312 . 314 and 316 As the current supplied changes, a measurement of the voltages can be used to change the temperature in the regions of the substrate 300 appreciate. Usually, the material used to form the webs, which is the current to the resistive elements 310 . 312 . 314 and 316 lead, is used, similar to the material containing the resistive elements 310 . 312 . 314 and 316 forms. Spatial restrictions on the substrate 300 and placement considerations for the resistive elements 310 . 312 . 314 and 316 and the tracks that they use with the power sources 318 . 320 . 322 and 324 pairing, that lead to the analog / digital converter 328 supplied analog voltages comprise an error component corresponding to the temperature-related changes in the resistance of the webs. In order to improve the effectiveness of the temperature compensation system utilizing the digital values corresponding to the measured voltages, an embodiment of the temperature measurement system reduces the contribution of the traces to the measured temperature changes in the voltage values.

In 4 is a schematic diagram shown that a section 332 of the 3 equivalent. Resistive elements 310 and 312 are implemented using serpentine routing of the tracks in the region corresponding to the resistive element to increase the proportion of total temperature resistance change (starting from the track and the serpentine resistive element) corresponding to the serpentine guided resistive element. The increase in the rate of temperature change in resistance corresponding to the resistive element is accomplished by increasing the path length associated with the resistive element. It should be appreciated that other possibilities, such as the rate of change in resistance of the resistive element due to temperature, could be used individually or in combination with increasing the path length. For example, by decreasing the width of the resistive element associated path, the rate of temperature change in resistance corresponding to the resistive element could be increased. Or, the portion of the temperature resistance of the web could be reduced (thereby increasing the rate of change in resistance associated with the resistive element) by increasing the width of the web, reducing the length of the web, or passing the web through regions physically on the substrate 300 are away from the firing resistors. By increasing the portion of the temperature-related total resistance change due to the resistive element, the error that the web contributes to the voltage value is reduced. It should be appreciated that other arrangements of resistive elements could be used to obtain a serpentine shape. For example, the resistive element could be patterned such that the serpentine pattern could be formed by a side-to-side pattern or a diagonal pattern rather than following the serpentine path in a top-to-bottom pattern, as in FIG 4 is shown.

Another way to increase the proportion of total temperature change in resistance associated with the resistive elements (or equivalently to reduce the amount of total temperature change in resistance corresponding to the traces) involves the use of materials suitable for the resistive elements and the tracks have a different temperature coefficient of resistivity. There are several ways to accomplish this. A first option involves using a material having a low temperature coefficient of resistivity for the web 326 relative to the material used for the resistive element. One such set of materials that could be used is a tantalum / aluminum alloy for the tracks and aluminum for the resistive elements. A tantalum / aluminum alloy has a temperature coefficient of resistivity that is considerably less than that of aluminum. For aluminum and a particular tantalum / aluminum alloy, the ratio of the aluminum TCR (TCR) to the TCR of the tantalum / aluminum alloy is about 37. It should be appreciated that other sets of materials, which have the desired relationship of the temperature coefficient of resistivity for which the web and the resistive element could be used to achieve the desired effect. The use of various materials for the web and the resistive element is disclosed in U.S. Pat 4 illustrated by the train 326 a dashed line and for the parts of the resistive element 310 and the resistive element 312 , in the 4 are shown, a solid line is used. Use of materials having this relationship between the temperature coefficient of resistivity for the web material and the material of the resistive elements causes a greater proportion of the temperature-related total resistance change to be contributed by the resistive element. In addition, since the resistivity of aluminum is less than that of the tantalum / aluminum alloy, controlling the geometry of the web and the resistive element allows the resistive element to be associated with an even greater percentage of the temperature-related total resistance change. With respect to aluminum and a particular tantalum / aluminum alloy, the ratio of the resistivity of aluminum to the resistivity of the tantalum / aluminum alloy is about 1/500. The cross-sectional area and length (for example, by efficient web guiding) of the web would be controlled to reduce the resistance of the web. The cross-sectional area and length (eg, following a serpentine path) of the resistive element would be controlled to increase the resistance of the resistive element.

A second option involves forming the web from two materials, the temperature coefficients have the resistivity, so that the resistance for the reversing two materials in opposite directions. By a use of two materials, the temperature coefficient of the specific Could have resistance with opposite signs, the Amount of temperature change of the resistivity can be reduced. One should emphasize that it is to take advantage of a use of materials too draw the coefficients of resistivity with opposite signs it is not necessary that they be caused by the materials temperature-related resistance changes To get picked up. It is advantageous to match the tracks temperature-induced resistance change merely to reduce (rather than eliminate).

In 5A a way is shown for the web of using two materials having temperature coefficients of resistivity of opposite sign 400 to implement. The different materials are used in alternating, serially connected segments of the web 400 used. Alternate segments of such a length would be used that the first and second materials are subjected to substantially the same average temperature over the entire length of the web. A first section 402 the train 400 is made of a first material, for. As tungsten / silicon / nitride (WSiN), which has a negative temperature coefficient of resistivity formed. A second section 404 the train 400 is made of a second material, for. For example, polysilicon having a positive temperature coefficient of resistivity is formed. The proportion of the total length of the web assigned to each of the two materials could be adjusted to reduce the temperature-induced change in resistance of the entire web. For example, if the first material had a negative temperature coefficient of resistivity of a smaller amount than the positive temperature coefficient of resistivity of the second material, a longer total length of the first material would be used so that a temperature-induced total resistance change of the web would be reduced or so selected, that it is essentially zero. The alternating segments of the first material and the second material would have a length and width which is selected to form pairs that provide at least partially compensating temperature changes in resistance. The relative lengths of segments of the first material and the second material of a given width which would form a segment pair could be determined by equating an amount of resistance changes, for a given temperature change, of each segment forming a segment pair. A temperature-induced increase in the resistance (which causes an increase in the voltage drop from the substantially constant current) in a segment formed from the first material would be due to a temperature-induced reduction of the resistance (which causes a decrease in the voltage drop from the same substantially constant current) at least partially balanced in the adjacent segment formed from the second material.

In 5B another possible implementation using the first material and the second material is shown. In the implementation of the 5B becomes the first material in a first segment 500 parallel to the second material in a second segment 502 used. The width of the first segment 500 and the second segment 502 would be selected to account for differences in the magnitude of the resistivity temperature coefficients, such that the amount of temperature-induced resistance change would be that resulting from parallel combining of the first segment 500 and the second segment 502 resulting web over a temperature range is reduced overall. Although the configuration of the 5B temperature induced changes in the resistance of the web may not be as effective as those in 5A nevertheless, it may be designed to provide a beneficial reduction in the amount of temperature change in resistance of the web over a range of temperatures. Consider the case where the first material corresponds to a material having a negative temperature coefficient of resistivity and the second material corresponds to a material having a positive temperature coefficient of resistivity. In addition, the width of the first segment 500 and the width of the second segment 502 selected so that the resistance of these tracks from one end to the other at a fixed temperature (for example, a nominal operating temperature of the substrate 300 ) is substantially the same. If the average temperature over the length of the combination of the first segment 500 and the second segment 502 would rise, the resistance of the first segment would increase 500 decrease, the resistance of the second segment would 502 increase and the delivered electricity would be split up so that more electricity passes through the first segment 500 and less through the second segment 502 flows. This would be the voltage increase that would occur when passing through the second segment 502 flowing electricity would not have changed, at least partially offset. If the average temperature over the length of the combination of the first segment 500 and the second segment 502 would decrease, take the resistance of the first segment 500 too, take the resistance of the second segment 502 off, and would the delivered electricity be split up so that more current flows through the second segment 502 and less through the first segment 500 flows. This would be the voltage reduction that would occur if the entire current were forced through the first segment 500 to flow, at least partially offset. You should realize that, although the first segment 500 and the second segment 502 shown as being placed in the same plane next to each other, so on the substrate 300 could be made that they lie on top of each other.

Claims (4)

An apparatus for determining the temperature of a printhead substrate, comprising: a substrate ( 300 ); a resistive element ( 310 ) projecting onto a first region of the substrate ( 300 ) is applied and from a first material ( 402 . 500 ) having a first temperature coefficient of resistivity; and characterized in that a pair of tracks ( 326 ) passing through the resistive element ( 310 ), each track being made up of a plurality of sections of a second material ( 404 . 502 ) having a second temperature coefficient of resistivity and formed of a second plurality of portions of a third material having a third temperature coefficient of resistivity. The device of claim 1, wherein: an amount of a temperature coefficient of resistivity of said pair of lanes ( 326 ) has a value less than an amount of the second temperature coefficient of resistivity and less than an amount of the third temperature coefficient of resistivity; and the first plurality of sections form a series connection with the second plurality of sections, wherein some of the first plurality of sections alternate with some of the second plurality of sections in the series circuit. The device of claim 1, wherein: an amount of a temperature coefficient of resistivity of said pair of lanes ( 326 ) has a value less than an amount of the second temperature coefficient of resistivity and less than an amount of the third temperature coefficient of resistivity; and each of the first plurality of sections is connected in parallel with a corresponding one of the second plurality of sections, thereby forming a plurality of section pairs, wherein the plurality of section pairs are connected in series. The device of claim 1, wherein: the second material ( 404 . 502 ) Polysilicon; the third material WSiN comprises; and the first plurality of sections form a series connection with the second plurality of sections, wherein some of the first plurality of sections alternate with some of the second plurality of sections in the series circuit.